System and method for zonal switching for light steering to produce an image having high dynamic range

ABSTRACT

A method and system for zonal switching for light steering to produce an image having high dynamic range is described. The system comprises: a light source for providing light along an optical path; a spatial light modulator for directing portions of the light to off-state and on-state light paths, thereby producing an image, the spatial light modulator having a plurality of illumination zones corresponding to the image; and a set of sequentially-arranged optical elements in the optical path for steering at least some of the light from a first subset of the plurality of illumination zones to a second subset of the plurality of illumination zones to increase the dynamic range of the image. The dwell time of the one or more sequentially arranged optical elements can be modified to steer light.

FIELD

The specification relates generally to projection systems, andspecifically to a system and method for zonal switching for lightsteering to produce an image having high dynamic range.

BACKGROUND

Current projection systems require that the illumination of the spatiallight modulator (SLM) be uniform over the entire SLM imaging surface. Inother words, the amount of light received by each pixel of the SLM isrequired by these systems to be generally equal, such that illuminationof the brightest areas is limited by the overall illumination of the SLMmirrors. This can result in an image that is not a true representationof the original or desired image, particularly if that original ordesired image constitutes an image having high dynamic range.

SUMMARY

According to one implementation, there is provided a system forproducing an image having high dynamic range, comprising: a light sourcefor providing light along an optical path; a spatial light modulator fordirecting portions of the light to off-state and on-state light paths,thereby producing an image, the spatial light modulator having aplurality of illumination zones corresponding to the image; and a set ofsequentially-arranged optical elements in the optical path for steeringat least some of the light from a first subset of the plurality ofillumination zones to a second subset of the plurality of illuminationzones to increase the dynamic range of the image.

According to another implementation, the system for producing an imagehaving high dynamic range further comprises an intermediary opticalelement for capturing and modulating the steered light according to theplurality of illumination zones. According to a related implementation,the modulation comprises homogenizing the steered light. According to arelated implementation, the intermediary optical element comprises anarray of integrating rods arranged to correspond to the plurality ofillumination zones.

According to another implementation, a dwell time of the one or moresequentially arranged optical elements is modified to steer light.According to a related implementation, modifying the dwell time modifiesa composition of the duty cycle of one or more sequentially arrangedoptical elements.

According to another implementation, one or more optical element of theset of sequentially-arranged optical elements spends a portion of a dutycycle steering the at least some of the light from the first subset tothe second subset to increase the dynamic range of the image. Accordingto a related implementation, the portion of the duty cycle correspondsto a light intensity level of a light intensity zone of the image.

According to another implementation, the set of sequentially-arrangedoptical elements comprises one or more rotatable mirrors. According to arelated implementation, at least one of the one or more rotatablemirrors is mounted on a gimbal.

According to an implementation, the set of sequentially-arranged opticalelements comprises one or more digital micro-mirror devices.

According to another implementation, the system for producing an imagehaving high dynamic range further comprises a drive system forconfiguring the spatial light modulator to produce the image based onimage content data; and wherein the drive system configures the set ofsequentially-arranged optical elements to steer the light to theplurality of illumination zones of the spatial light modulator based onthe image content data.

According to another implementation, the light source comprises a laserlight module.

According to another implementation, the light source comprises at leastone of a light emitting diode and a laser-phosphor hybrid light source.

According to another implementation, the light source comprises a lamp.

According to another implementation, the system for producing an imagehaving high dynamic range further comprises light collimating optics.

According to another implementation, the spatial light modulatorcomprises a digital micromirror device.

According to another implementation, the spatial light modulatorcomprises a liquid crystal device.

According to one implementation, there is provided a method forproducing an image having high dynamic range, comprising: providinglight along an optical path; steering the light by one or moresequentially arranged optical elements to increase the dynamic range ofan image; and directing the light to produce an image.

According to one implementation, the steering further comprisingmodifying a dwell time of the one or more sequentially arranged opticalelements.

According to one implementation, the method for producing an imagehaving high dynamic range further comprises modifying a composition ofthe duty cycle of one or more sequentially arranged optical elements.

BRIEF DESCRIPTIONS OF THE DRAWINGS

For a better understanding of the various implementations describedherein and to show more clearly how they may be carried into effect,reference will now be made, by way of example only, to the accompanyingdrawings in which:

FIG. 1 depicts a schematic representation of a projection system,according to prior art implementations.

FIG. 2 a depicts a desired image to be projected by a digital projectionsystem according to prior art implementations.

FIG. 2 b depicts a front view of a representative spatial lightmodulator (SLM) configured to produce the desired image of FIG. 2 a,according to prior art implementations.

FIG. 2 c depicts the desired image as produced by the SLM of FIG. 2 c.

FIG. 3 depicts an image having high dynamic range that is to beprojected according to non-limiting implementations.

FIG. 4 depicts a system for producing an image having high dynamicrange, according to non-limiting implementations.

FIG. 5 depicts a system for producing an image having high dynamicrange, according to non-limiting implementations.

FIG. 6 depicts a flowchart of a method for producing an image havinghigh dynamic range, according to non-limiting implementations.

DETAILED DESCRIPTION

FIG. 1 depicts a schematic representation of prior art projection system100. Projection system 100 comprises light source 105 that provides(e.g. transmits) light 110 along optical path 115. According to someimplementations, light source 105 comprises a lamp, such as a Xenon lampand a parabolic reflector. According to some implementations, lightsource 105 comprises a laser light module. Light 110 is transmitted tointermediate optics 120. Intermediate optics 120 manipulates light 110to produce light cones 125 a, 125 b and 125 c, referred to collectivelyas light cones 125 and depicted as arrows for simplicity. Intermediateoptics 120 can include, for example, one or more integrating rods,prisms, relay lenses and mirrors. It is understood that light 110comprises the light of light cones 125 a, 125 b and 125 c. In otherwords, light cones 125 a, 125 b and 125 c are portions or subsets oflight 110. It is understood that “manipulating light” (and theequivalent) can include, for example, one or more of collecting,homogenizing, filtering and relaying light.

Each of light cones 125 a, 125 b and 125 c is provided along arespective optical path 130 a, 130 b and 130 c (also referred to aslight paths 130 a, 130 b and 130 c). Although optical paths 115 and 130b appear to be at least initially parallel, according to someimplementations, none of light cones 125 a, 125 b and 125 c have anoptical path that is collinear with optical path 115. Alternatively,according to some implementations, one or more of optical paths 130 a,130 b and 130 c may be collinear with optical path 115. Furthermore,although only three light cones are depicted in FIG. 1, according tosome implementations two or more light cones, including more than threelight cones, are transmitted by intermediate optics 120.

It will be understood that the terms “light path” and “optical path” areused herein to denote the path along which light can and may travel inthe system. As a result, unless otherwise indicated, the terms “lightpath” and “optical path” will be considered interchangeable with eachother.

Light cones 125 are transmitted to Spatial light modulator (SLM) 135.SLM 135 can be provided by, for example, Texas Instruments™. Forsimplicity, SLM 135 is depicted as having three mirrors, referred toindividually as mirrors 140 a, 140 b and 140 c and collectively asmirrors 140, for receiving light, such as light cones 125, and producingan image based upon at least one received light cone. Each one of themirrors 140 corresponds to a pixel of the produced image. According tosome implementations, SLM 135 will have more than three mirrors arrangedin a grid pattern. For example, SLM 135 can be a 4K resolution SLMhaving a resolution of 4096×2160 pixels and over 8 million micro-mirrorsin a grid pattern.

Mirrors 140 can be independently switched (i.e. actuated) to anOFF-state, in which the received light is not transmitted to projectionoptics 165, and an ON-state, in which the received light is transmittedto projection optics 165. For example, as depicted in FIG. 1, light cone125 a is received by mirror 140 a, which directs the received light cone125 a towards light dump 150. Since optical path 130 a is an optical orlight path light cone 125 a travels or is transmitted along to anOFF-state SLM mirror (mirror 140 a), optical path 130 a will beconsidered an OFF-state optical or light path. In other words, by virtueof being an optical or light path destined for an OFF-state SLM mirroror region other than for being transmitted to projection optics 165(such as directly to a light dump 150), such an optical or light path isconsidered, for the purposes of this disclosure, to be an OFF-stateoptical or light path. According to some implementations, one or more ofSLM mirrors 140 b and 140 c are switched to an OFF-state, which wouldthen result in the respective one or more optical paths 130 b and 130 cbecoming OFF-state optical or light path(s). According to someimplementations, mirror 140 a is switched to an ON-state, which wouldthen result in optical path 130 a becoming an ON-state light path.

In a SLM imaging device, such as prior art projection system 100 and asexemplified by the Digital Light Processing (DLP™) technology of TexasInstruments, the dynamic range of a projected image is limited by theswitching speed of the SLM, and by said systems' ability to segregateOFF-state light from the projection path. Grey scale aspects of theimage are created using pulse width modulation (PWM) techniques. Thus,for a SLM device full white is achieved by leaving the SLM mirrors, suchas mirrors 140 a, 140 b and 140 c, in the ON-state for the duration ofthe SLM mirror duty cycle, full black is achieved by leaving the mirrorsin the OFF-state for the SLM mirror duty cycle, while minimal grey isachieved by having the mirrors in the ON-state for the shortest periodof time during the SLM duty cycle that can be supported by the SLM. Inother words, the portion of the duty cycle each SLM mirror spends in aparticular state dictates the intensity (“brightness”) of the pixel.

Light cones 125 b and 125 c are received and directed by mirrors 140 b,140 c to projection optics 165 where the resulting image may beprojected onto a screen (not shown). Contrary to optical path 130 a,since optical paths 130 b and 130 c are optical or light paths alongwhich light cones 125 b and 125 c travel or are transmitted to anON-state SLM mirror (mirrors 140 b, 140 c), optical paths 130 b and 130c are considered, in the system 100, to be ON-state optical or lightpaths. Although FIG. 1 depicts each one of light cones 125 a, 125 b and125 c being received and directed by a different one of mirrors 140 a,140 b and 140 c, in some implementations, each one of mirrors canreceive and direct more than one of light cones 125 a, 125 b and 125 c.Projection system 100 further includes drive system 170 in communicationwith SLM 135 via communication path 175. Drive system 170 configures SLM135 to produce an image by, for example, switching mirrors 140 betweenan ON-state and an OFF-state based on the above-described PWMtechniques.

Projection system 100 may also include additional light dumps oranalogous devices (not shown) to absorb any light spillage from lightcones 125 as received or directed by SLM 135 via mirrors 140.Furthermore, projection system 100 can comprise additional lightdirecting and/or directing devices specifically included for the purposeof directing light to OFF-state light paths or regions. For example,projection system 100 can include an additional SLM to help direct lightOFF-state.

Reference is now made to FIGS. 2 a, 2 b and 2 c, depicting desired image200, SLM 205 and image 210, produced by SLM 205, to illustratedisadvantages of prior art projection systems, such as projection system100. SLM 205 includes set of mirrors 215 comprised of mirrors 215(1,1)to 215 (8,8). It would be understood that the configuration of the setof mirrors 215 is not limited to an 8×8 configuration, but any suitableconfiguration of mirrors 215 can be used. Each one of mirrors 215(1,1)to 215 (8,8) corresponds to a pixel of image 210.

As shown in FIG. 2 a, desired image 200 includes both bright and darkareas (or zones). In order to produce an image based upon desired image200, SLM 205, and particularly mirrors 215(1,1) to 215 (8,8) areactuated to direct the received light to OFF-state and ON-state opticalpaths. Dark zones of desired image 200 (e.g. Zone C) correspond toOFF-state mirrors (e.g. mirrors 215(4,1), 215(4,2), 215(5,1) and215(5,2)) and bright zones (e.g. Zone D) correspond to ON-state mirrors(e.g. mirrors 215(6,2) to 215(6, 7) and 215(7,3) to 215(7,6)) of the setof mirrors 215.

Prior art projection systems and devices, such as projection system 100and SLM 205, require that the illumination of the SLM be uniform overthe entire SLM imaging surface. In other words, the amount of lightreceived by each mirror of the SLM (e.g. mirrors 140 and 215(1,1) to 215(8,8)) is required by these systems to be generally equal. This resultsin the illumination of the brightest areas being limited by the overallillumination of the SLM mirrors. This may, in some cases, not result inan image that is a true representation of the original or desired image,particularly if that original or desired image constitutes an imagehaving high dynamic range. For example, in image 210 produced by SLM205, the brightest areas (represented by the hashed lines) are not asbright as the brightest areas of desired image 200.

Attention is directed to FIG. 3, which depicts high dynamic range image300 (also referred herein as “image 300”) to be projected, according tonon-limiting implementations, such as system 400 depicted in FIG. 4.Image 300 has four zones of light intensity, Zone 1, Zone 2, Zone 3 andZone 4. As shown, Zone 1 has the greatest light intensity, followed byZone 2, which is followed by Zone 3 and Zone 4 (having the least amountof light intensity). In other words, Zone 1 represents the bright zoneof image 300, Zone 2 represents the second brightest zone of image 300,Zone 3 represents the third brightest zone of image 300 and Zone 4represents the least bright zone of image 300 (i.e. the darkest zone ofimage 300). It is understood that although image 300 is illustrated ashaving four zones of light intensity, according to some implementations,image 300 can have one or more zones of light in various configurations.

Current projection systems, such as prior art projection system 100, areunable to shift light from illumination areas or zones of the SLMimaging surface that are to show low-level (dark) content to thoseillumination areas or zones that are to show high-level (bright)content. As a result, much of the light that is provided or generated bythe light source is discarded (e.g. sent to a light dump). This leads toinefficient use of power, increased thermal load from discarded light,poor contrast and brightness performance amongst other effects.

As will be presently understood, herein described is a system forproducing an image having a high dynamic range that utilizes a set ofsequentially-arranged light steering devices to direct light into one ofseveral illumination zones of the SLM. As a result, the incident lightis not distributed evenly across the SLM. The provided light can bedivided as the system requires since the light steering devices can haveswitching times that are faster than the framerate of the content.

Attention is directed to system 400 for producing an image havingdynamic range, such as image 300, according to non-limitingimplementations. System 400 comprises SLM 440 for directing portions oflight to OFF-state and ON-state light paths, thereby producing image300. Furthermore, SLM 440 is divided into a plurality of illuminationzones in which each illumination zone corresponds to a light intensityzone of image 300. Since image 300 has four light intensity zones, SLM440 is divided into four illumination zones. The term “illuminationzone” as used herein, refers to an area of the SLM imaging surface (i.e.the SLM mirrors) that receive light for producing an image. Forsimplicity, each the four illumination zones are represented by mirrors440 a, 440 b, 440 c and 440 d, where: mirror 440 a represents one ormore SLM mirrors configured to correspond to Zone 1, mirror 440 brepresents one or more SLM mirrors configured to correspond to Zone 2,mirror 440 c represents one or more SLM mirrors configured to correspondto Zone 3 and mirror 440 d represents one or more SLM mirrors configuredto correspond to Zone 4. For example, SLM 440 can be a 4K resolution SLMhaving a resolution of 4096×2160 pixels and over 8 million micro-mirrorsin a grid pattern. In this example, each one of mirrors 440 a, 440 b,440 c and 440 d represents 2 million micro-mirrors. It is understoodthat SLM 440 could be divided into a variety of illumination zones ofdiffering arrangements, depending on the arrangement of the lightintensity zones and desired image characteristics of the image to beproduced. Although in this implementation the 440 are shown in a lineararrangement, in variations, the shape of the arrangement can vary.

SLM 440 can comprise a wide range of light modulating devices,including, for example, a digital micromirror device (DMD) and a liquidcrystal device (LCD).

Furthermore, it is understood that each of the illumination zonesrepresented by mirrors 440 a, 440 b, 440 c and 440 d is switched usingPWM to achieve the appropriate light intensity of Zone 1, Zone 2, Zone 3and Zone 4 as per image 300. In FIG. 4, mirror 440 d is shown in theOFF-state, since it is directing received light away from projectionoptics, towards light dump 460. Mirrors 440 a, 440 b and 440 c are shownin an ON-state to direct received light to projection optics 460 a.

System 400 further comprises light source 405 for providing light 410along optical path 415. According to some implementations, light source405 comprises a lamp, such as a Xenon lamp having a parabolic reflector.According to some implementations, light source 405 comprises a laserlight module. According to some implementations, the light source cancomprise at least one of a light emitting diode (LED) and alaser-phosphor hybrid light sources. According to some implementations,light 410 is transmitted to intermediary optics 415 to modulate light410. For example, intermediary optics 415 can comprise one or moreoptical elements for collimating light 410. According to someintermediary optics 415 can include, for example, one or moreintegrating rods, prisms, relay lenses and mirrors. Intermediary optics415 transmits (i.e. outputs) modulated light 420. It is understood thatmodulated light 420 comprises light 410. However, it is understood thatintermediary optics 415, and the therefore the resulting lightmodulation, is not necessary for operation of the systems describedherein. Therefore, although reference herein is made to “modulated light420”, according to some implementations the referenced “modulated light420” can comprise light 410 without any modulation applied thereto.Furthermore, according to some implementations, “modulated light 420”comprises light 410 that has been manipulated, as defined above, ratherthan modulated. According to some implementations, “modulated light 420”comprises light 410 that has been both modulated and manipulated (asdefined above).

Modulated light 420 is transmitted to a set of sequentially-arrangedoptical elements 425 in optical path 415 for steering at least some ofmodulated light 420 from a first subset of illumination zones (Zone 1,Zone 2, Zone 3, Zone 4) to a second subset of illumination zones (Zone1, Zone 2, Zone 3, Zone 4) to increase the dynamic range of an image. Inthe implementation shown in FIG. 4, modulated light 420 is received byoptical element 425 a. Similar to a “pinball”, optical element 425 aeither directs modulated light 420 to optical element 425 b or directsmodulated light 420 to optical element 425 c. According to someimplementations, optical element 425 a is rotatable to direct themodulated light 420. For example, according to some implementations,optical element 425 a is mounted on a pivoted support, such as a gimbal.According to some implementations, optical element 425 a comprises aspatial light modulator (SLM). For example, optical element 425 a cancomprise a low resolution SLM.

Although the set of sequentially-arranged optical elements 425 is shownin FIG. 4 as comprising only three optical elements (425 a, 425 b, 425c), according to some implementations, the set of sequentially-arrangedoptical elements 425 comprises more than three optical elements arrangedin a tree-structure such that every “branch” (represented by an opticalelement, or a subset of optical elements) directs modulated light 420 toa respective illumination zone on SLM 440. For example, the set ofsequentially-arranged optical elements 425 can comprise 7 opticalelements. Accordingly, in this example, the elements 425 b and 425 cwould direct modulated light to one of additional four optical elements,providing at least eight illumination zones. According to someimplementations, each of the sequentially arranged optical elements 425can steer light in more than two directions. Accordingly, in theseimplementations, optical element 425 a can steer light, for example, tofour different optical elements to achieve the “pinball” effect. In someimplementations, each of the sequentially arranged optical elements cansteer light in a different number of directions. Moreover, invariations, the number of directions light can be steered by eachsequentially arranged optical element can be varied dynamically, thusaltering the number and arrangement of zones.

Modulated light 420 is then directed to second intermediary opticalelement 435 along one of optical paths 430 a, 430 b, 430 c and 430 d byeither optical element 425 b or 425 b. According to someimplementations, one or more of optical elements 425 b and 425 c arerotatable to direct modulated light to a respective one of optical paths430 a, 430 b, 430 c and 430 d. For example, according to someimplementations, one or more of optical elements 425 b and 425 c aremounted on a pivoted support, such as a gimbal. According to someimplementations, one or more of optical elements 425 b and 425 ccomprise a spatial light modulator (SLM). For example, one or more ofoptical elements 425 b and 425 c can comprise a low resolution SLM.

According to some implementations, system 400 further comprises secondintermediary optical element 435 for capturing and further relayingmodulated light 420. For example, second intermediary optical element435 can homogenize modulated light 420. Second intermediary opticalelement 435 directs the further modulated light as one of modulatedlight 445 a, 445 b, 445 c and 445 d along a respective optical path. Forexample, to produce Zone 4 of image 300, the darkest zone, modulatedlight received by Zone 435 d is directed as modulated light 445 d alongoptical path 450 d to light dump 460 (rather than projection optics465). It is understood, that since Zone 4 has the least amount of lightintensity in comparison to the remaining three zones, the least amountor proportion of light 410 will be directed to Zone 435 d and mirror 440d. In contrast, since Zone 1 has the greatest amount of light intensity,the greatest amount or proportion of light 410 will be directed to Zone435 a and mirror 445 a.

As illustrated in FIG. 4, second intermediary optical element 435 isdivided into four zones, each zone corresponding to an illumination zoneof SLM 440. Zone 435 a corresponds to the illumination zone representedby mirror 440 a, Zone 435 b corresponds to the illumination zonerepresented by mirror 440 b, Zone 435 c to the illumination zonerepresented by mirror 440 c and Zone 435 d corresponds to theillumination zone represented by mirror 440 d. According to someimplementations, second intermediary optical element 435 comprises anarray of integrating rods.

The amount or proportion of light 410 received by any one of theillumination zones represented by mirrors 440 a, 440 b, 440 c and 440 d,and therefore the light intensity of the associated zone of image 300,can be controlled by adjusting the amount of time each optical element425 a, 425 b and 425 c spends during its respective duty cycle directingmodulated light 420 to any one of the illumination zones represented bymirrors 440 a, 440 b, 440 c and 440 d.

Drive system 470 configures SLM 440 to produce the image based on imagecontent data 485. Drive system 470 is in communication with SLM 440 viacommunication path 475. According to some implementations, drive system470 is in two-way communication with SLM 440 (i.e. drive system 470 cancommunicate or transmit data to SLM 440 and, vice-versa, SLM 440 cancommunicate or transmit data to drive system 470). According to someimplementations, the communication between drive system 470 and SLM 440is one-way. However, any suitable manner of communication between drivesystem 470 and SLM 440 is contemplated. For example, drive system 470can be remote from SLM 440 and communicate with SLM 440 wirelessly. Inanother example, drive system 470 and SLM 440 can be connected via wiredconnection and/or mechanical connection. Furthermore, although FIG. 4depicts a particular path for communication between drive system 470 andSLM 440, it is contemplated that communication path 475 comprises any ofone or more communication paths suitable for communication between drivesystem 470 and SLM 440. For example, communication path 475 can compriseany combination of wired and/or wireless communication paths as desired.

Drive system 470 also configures the set of sequentially-arrangedoptical elements 425 to steer at least some for steering at least someof modulated light 420 from a first subset of illumination zones (Zone1, Zone 2, Zone 3, Zone 4) to a second subset of illumination zones(Zone 1, Zone 2, Zone 3, Zone 4) based on image content data 485. Drivesystem 470 is in communication with the set of sequentially-arrangedoptic al elements 425 via communication path 480. According to someimplementations, drive system 470 is in two-way communication with theset of sequentially-arranged optical elements 425 (i.e. drive system 470can communicate or transmit data to the set of sequentially-arrangedoptical elements 425 and, vice-versa, the set of sequentially-arrangedoptical elements 425 can communicate or transmit data to drive system470). According to some implementations, the communication between drivesystem 470 and the set of sequentially-arranged optical elements 425 isone-way. However, any suitable manner of communication between drivesystem 470 and the set of sequentially-arranged optical elements 425 iscontemplated. For example, drive system 470 can be remote from the setof sequentially-arranged optical elements 425 and communicate with theset of sequentially-arranged optical elements 425 wirelessly. In anotherexample, drive system 470 and the set of sequentially-arranged opticalelements 425 can be connected via wired connection and/or mechanicalconnection. Furthermore, although FIG. 4 depicts a particular path forcommunication between drive system 470 and the set ofsequentially-arranged optical elements 425, it is contemplated thatcommunication path 480 comprises any of one or more communication pathssuitable for communication between drive system 470 and the set ofsequentially-arranged optical elements 425. For example, communicationpath 480 can comprise any combination of wired and/or wirelesscommunication paths as desired.

According to some implementations, drive system 470 comprises acomputing device having a processor to configure SLM 440 and the set ofsequentially-arranged optical elements 425 based on image content data485. According to some implementations, image content data 485 is storedat a local memory device of drive system 470. According to someimplementations, image content data 485 is transmitted to drive system470 or retrieved by drive system 470 from another device via a wired orremote connection.

As a non-limiting example implementation, image content data 485 cancomprise a frame of image content having data for all three primarycolours and the number of zones of light intensity of the image to beproduced. In some cases, the frame of image content could be separatedinto red, blue and green wavelengths of light, corresponding to thethree primaries of projection system 400. Each such separated frame ofimage content will be referred to herein, for the purpose of thisnon-limiting example, as a “subframe”. Hence, in this example, there arethree subframes, one for each portion of the frame of image contentcorresponding to a primary colour wavelength of light (e.g. a red lightsubframe). However, it is understood that it is not necessary for theframe of image content be separated into red, blue and green wavelengthsof light.

In this non-limiting example, each one of the subframes (e.g. the redlight subframe) is divided into four light intensity zones of the imageto be produced (e.g. Zone 1, Zone 2, Zone 3 and Zone 4 of image 300).Each one of the four light intensity zones will correspond to one ofoptical paths 430 a, 430 b, 430 c and 430 d that modulated light 420 isdirected along by the set of sequentially-arranged optical elements 425to one of Zones 435 a, 435 b, 435 c and 435 d, and to, ultimately, oneof the illumination zones represented by mirrors 440 a, 440 b, 440 c and440 d. In this non-limiting example, the light intensity zones will haveequal width and height.

For each one of the light intensity zones of the image, the pixelcorresponding to the brightest spot in that light intensity zone isdetermined. In other words, the mirror in each illumination zonerepresented by mirrors 440 a, 440 b, 440 c and 440 d that corresponds tothe brightest spot in the corresponding light intensity zone, and thecorresponding optical path of optical paths 430 a, 430 b, 430 c and 430d along which modulated light 420 is directed, is determined. Since,ideally, for a particular light intensity zone only enough light toproperly illuminate this pixel is provided to that particularillumination zone, the amount of light (i.e. light intensity) requiredto properly illuminate the brightest pixel corresponds to the amount oflight that is required to be provided to the entire zone.

In this example, since there are four light intensity zones, for eachsubframe there will be four “brightest pixels” (one “brightest pixel”for each light intensity zone). For the purposes of this non-limitingexample, the light intensity associated with each “brightest pixel” willbe referred to herein as “P_(a)” (the light intensity associated withthe brightest spot located in Zone 1), “P_(b)” (the light intensityassociated with the brightest spot located in Zone 2), “P_(a)” (thelight intensity associated with the brightest spot located in Zone 3)and “P_(d)” (the light intensity associated with the brightest spotlocated in Zone 4).

Next, for simplicity, the light intensity of P_(a), P_(b), P_(c) andP_(d) is normalized to become P_(a)′, P_(b)′, P_(c)′ and P_(d)′ suchthat

P _(a) ′+P _(b) ′+P _(c) ′+P _(d)′=1  (1)

For example,

$\begin{matrix}{P_{a}^{\prime} = \frac{P_{a}}{P_{a} + P_{b} + P_{c} + P_{d}}} & (2)\end{matrix}$

Where each of P_(a)′, P_(b)′, P_(c)′ and P_(d)′ in equation (1)represents the light intensity of P_(a), P_(b), P_(c) and P_(d)expressed in a fraction of the total light delivered to mirrors 440 a,440 b, 440 c and 440 d. Although in this example the light intensity ofP_(a), P_(b), P_(c) and P_(d) is normalized, it is understood that theexample implementation can be performed without such normalization.

Each one of optical elements 425 a, 425 b and 425 c will divide theperiod of a duty cycle, such as L referred to above, into portions orfractions of that duty cycle for directing modulated light 420 such thatit is directed along one of optical paths 430 a, 430 b, 430 c and 430 d.For example, optical element 425 a can spend portion of time “α”, as afraction of L having a value of 1, directing modulated light 420 towardsoptical element 425 c and portion of time (1-α) directing modulatedlight 420 towards 420 b.

In this non-limiting example, optical element 425 c will divide dutycycle, L, into three parts, A, B and C. “A” represents the time in whichoptical element 425 c does not receive modulated light 420 from opticalelement 425 a (i.e. optical element 425 a is not directing modulatedlight 420 to optical element 425 c) and can therefore be in anystate/position. In this case, “A” represents (1-α) of L. “B” representsthe time in which optical element 425 c is receiving modulated light 420from optical element 425 a (i.e. optical element 425 a is directingmodulated light 420 to optical element 425 c) and directs modulatedlight 420 along optical path 430 d to Zone 435 d. In this case, “B”represents (α*β) of L, where “β” represents a fraction of the portion ofduty cycle L in which optical element 425 c receives light from opticalelement 425 a. “C” represents the time in which optical element 425 c isreceiving modulated light 420 from optical element 425 a (i.e. opticalelement 425 a is directing modulated light 420 to optical element 425 c)and directs modulated light 420 along optical path 430 c to Zone 435 c.In this case, “C” represents (α*(1-β)) of L.

It is understood that the light intensity of a zone of an image isproportional to the time the corresponding illumination zone of the SLMis illuminated. As a result, it can be written:

P _(d)′=αβ  (3)

P _(c)′=α(1-β)  (4)

P _(b)′=(1-α)γ  (5)

P _(a)′=(1-α)(1-γ)  (6)

Since the values of P_(a)′, P_(b)′, P_(c)′ and P_(d)′ are known (seeequations 1 and 2), α, β and γ can be written as:

$\begin{matrix}{\alpha = {{1 - ( {P_{a}^{\prime} + P_{b}^{\prime}} )} = ( {P_{c}^{\prime} + P_{d}^{\prime}} )}} & (7) \\{\beta = \frac{P_{d}^{\prime}}{P_{c}^{\prime} + P_{d}^{\prime}}} & (8) \\{\gamma = \frac{P_{b}^{\prime}}{P_{a}^{\prime} + P_{b}^{\prime}}} & (9)\end{matrix}$

As a further non-limiting example, in a case where the four brightestpixels in the image can be described as P_(a,)=1 P_(b)=1, P_(c)=3 andP_(d)=5, based on equations (1) and (2), the normalized values of P_(a),P_(b), P_(c) and P_(d) would be approximately 0.1 (for P_(a)′), 0.1 (forP_(b)′), 0.3 (for P_(c)′) and 0.5 (for P_(d)′). Based on equations 7, 8and 9, the values of α, β and γ would be approximately 0.8 (α), 0.625(β) and 0.5 (γ). Schematically, the duty cycle, L, would be divided asshown in Table 1, Table 2 and Table 3.

TABLE 1 Division of Duty Cycle of Optical Element 425a Duty Cycle of425a Direct Light Toward 425b Direct Light Toward 425c 20% 80% (1 − α)(α)

TABLE 2 Division of Duty Cycle of Optical Element 425b Duty Cycle of425b Direct Light Direct Light Indeterminate State Toward 430a Toward430b (no Illumination) 10% 10% 80% (1 − α)(1 − γ) (1 − α)γ

TABLE 3 Division of Duty Cycle of Optical Element 425c Duty Cycle of425c Indeterminate State Direct Light Direct Light (no Illumination)Toward 430c Toward 430d 20% 30% 50% α(1 − β) (αβ)

It is understood that the values stated in the above non-limitingexamples are representative of the ideal case since, for simplicity,light losses and other losses have not been taken into account in thesenon-limiting examples.

Attention is directed to FIG. 5, depicting system 500 for producing animage having high dynamic range according to non-limitingimplementations and comprising elements similar to FIG. 5, with likeelements having like numbers, however starting with a “5” rather than a“4”. For example, system 500 includes a light source 505 which providesor transmits light 510 along optical path 515. As in system 400, SLM 540is divided into a plurality of illumination zones, each one of theilluminating zone corresponding to a zone of light intensity of an imageto be produced by SLM 540. Similar to SLM 440, SLM 540 is divided intofour illumination zones. For simplicity, each the four illuminationzones are represented by mirrors 540 a, 540 b, 540 c and 540 d, where:mirror 540 a represents one or more SLM mirrors configured to correspondto a first zone of illumination, mirror 540 b represents one or more SLMmirrors configured to correspond to a second zone of illumination,mirror 540 c represents one or more SLM mirrors configured to correspondto a third zone of illumination and mirror 540 d represents one or moreSLM mirrors configured to correspond to a fourth zone of illumination.

As stated above, the amount or proportion of light 510 received by anyone of the illumination zones represented by mirrors 540 a, 540 b, 540 cand 540 d, and therefore the light intensity of the associated zone ofthe produced image, can be controlled by adjusting the amount of timeoptical elements 525 a, 525 b and 525 c spends during its respectiveduty cycle directing modulated light 520 to any one of the illuminationzones represented by mirrors 540 a, 540 b, 540 c and 540 d. In otherwords, the time each one of optical elements 525 a, 525 b and 525 cspend directing modulated light 520 to one of the illumination zonesrepresented by mirrors 540 a, 540 b, 540 c and 540 d, also referredherein as the “dwell time” of optical elements 525 a, 525 b, 525 c and525 d, corresponds to the intensity of the corresponding light intensityzone of the image. Accordingly, the steering of light can beaccomplished by altering the composition of the duty cycle of an opticalelement 525 by varying the time each one of optical elements 525 a, 525b and 525 c spend directing modulated light 520 to one of theillumination zones.

As a non-limiting example, if system 500 is configured to produce animage having three zones of equal light intensity (corresponding to theillumination zones represented by mirrors 540 a, 540 b and 540 c) andone zone having minimal or zero light intensity (i.e. full black)(corresponding to the illumination zone represented by mirror 540 d),then the amount of light 510 provided during a particular time periodcan be, for example, divided by three and distributed evenly among theillumination zones of SLM 540.

In order to accomplish this light distribution, optical element 525 awould spend approximately one third of its duty cycle, referred to as“L”, directing modulated light 520 to optical element 525 b and theremaining two-thirds of L directing modulated light 520 to opticalelement 425 c. Since optical element 525 b directs modulated light 520to two of the three illumination zones of SLM 540 corresponding to zonesof equal light intensity of the image, optical element 525 b directsapproximately half of the received modulated light 520 to mirror 540 a(via Zone 535 a of second intermediary optical element 535) and directsthe remaining half of the received modulated light 520 to mirror 540 b(via Zone 535 b of second intermediary optical element 535). In otherwords, optical element 525 b spends approximately one-third of the dutycycle, L, of optical element 525 a directing received modulated light520 to mirror 540 a and approximately one-third of the duty cycle, L, ofoptical element 525 a directing received modulated light 520 to mirror540 b.

On the other hand, since optical element 525 b directs modulated light520 to only one of the three illumination zones of SLM 540 correspondingto zones of equal light intensity of the image, optical element 525 bdirects all of the received modulated light 520 to mirror 540 c (viaZone 535 c of second intermediary optical element 535). In other words,optical element 525 c spends approximately one third of L directingreceived modulated light 520 to mirror 540 c. Since the zone of lightintensity corresponding to the illumination zone represented by mirror540 d is full black, optical element 525 d does not spend any portion ofL directing any light to mirror 540 d.

Attention is now directed to FIG. 6 which depicts a flowchart of method600 for producing an image having high dynamic range, according tonon-limiting implementations. In order to assist in the explanation ofmethod 600, it will be assumed that method 600 is performed using system400. Furthermore, the following discussion of method 600 will lead to afurther understanding of system 400 and its various components. However,it is to be understood that system 400 and/or method 600 can be varied,and need not work exactly as discussed herein in conjunction with eachother, and that such variations are within the scope of presentimplementations. Furthermore, it will be understood that method 600 canbe implemented by systems 400 and 500.

It is to be emphasized, however, that method 600 need not be performedin the exact sequence as shown, unless otherwise indicated; and likewisevarious blocks may be performed in parallel, for example, rather than insequence; hence the elements of method 600 are referred to herein as“blocks” rather than “steps”. It is also to be understood, however, thatmethod 600 can be implemented on variations of systems 400 and 500 aswell. For example, method 600 could employ a set ofsequentially-arranged optical elements comprising more than threeoptical elements.

At block 605, light is provided along an optical path. For example,light 410 is provided by light source 405 along optical path 415.

At block 615, at least some of the light is steered from a first subsetof a plurality of illumination zones to a second subset of a pluralityof illumination zones to increase the dynamic range of the image. Forexample, referring to FIG. 4, the imaging surface of SLM 440 is dividedinto illumination zones corresponding to light intensity zones of image300. As stated above, mirror 440 a represents one or more SLM mirrorsconfigured to correspond to Zone 1, mirror 440 b represents one or moreSLM mirrors configured to correspond to Zone 2, mirror 440 c representsone or more SLM mirrors configured to correspond to Zone 3 and mirror440 d represents one or more SLM mirrors configured to correspond toZone 4.

Continuing with the present example, optical element 425 c can steermodulated light 420 away from mirror 440 d, where modulated light 420,following OFF-state light path 450 d, would have been directed to lightdump 460, to mirror 440 c, where modulated light 420 will be directedalong ON-state light path 450 c to projection optics 465. Since agreater portion of light 410 is being steered along an ON-state lightpath, more light overall is contributing to the light intensity of theassociated light intensity zone. As a result, the dynamic range of theimage is increased in comparison to an image produced by prior artprojection systems, such as prior art projection system 100.

At block 610, portions of the provided light are directed to OFF-stateand ON-state light paths according to illumination zones correspondingto an image, thereby producing an image. Modulated light 445 a, 445 band 445 c is directed by respective mirrors 440 a, 440 b and 440 c alongON-state light paths 450 a, 450 b and 450 c to projection optics 465.Modulated light 445 d is directed by mirror 440 d along OFF-state lightpath 450 d to light dump 460.

Systems 400 and 500 can yield many advantages. First, since no area orzone of the SLM imaging surface received more light than it requires,there is less need to dump excess light. In turn, this means thatunnecessary light is not generated, resulting in a more efficientsystem. Second, the described systems and methods can also result inbetter thermal management over prior art projection systems. Since thereis less light being directed OFF-state, and dumped, less thermal energyneeds to be removed. Likewise, since the SLM imaging surface receivesonly the light energy it needs, less energy is converted to heat on theSLM imaging surface. Third, the darkest areas receive less light, theywill appear darker on the screen, thus leading to higher contrastlevels. As a result, the lowest-achievable black level can be much lowerthan in projection systems without light steering. Finally, thedescribed systems and methods can yield improved highlight levels sincethe bright levels will be displayed with enhanced brightness. Utilizingthe described light steering systems and methods can allow for a subsetof pixels on the SLM imaging surface to project more light than wouldhave been possible has the light been distributed uniformly.

Persons skilled in the art will appreciate that there are yet morealternative implementations and modifications possible, and that theabove examples are only illustrations of one or more implementations.The scope, therefore, is only to be limited by the claims appendedhereto.

What is claimed is:
 1. A system for producing an image having highdynamic range, comprising: a light source for providing light along anoptical path; a spatial light modulator for directing portions of thelight to off-state and on-state light paths, thereby producing an image,the spatial light modulator having a plurality of illumination zonescorresponding to the image; and a set of sequentially-arranged opticalelements in the optical path for steering at least some of the lightfrom a first subset of the plurality of illumination zones to a secondsubset of the plurality of illumination zones to increase the dynamicrange of the image.
 2. The system of claim 1 further comprising: anintermediary optical element for capturing and modulating the steeredlight according to the plurality of illumination zones.
 3. The system ofclaim 2, wherein the modulation comprises homogenizing the steeredlight.
 4. The system of claim 1 wherein a dwell time of the one of moresequentially arranged optical elements is modified to steer light. 5.The system of claim 4 wherein modifying the dwell time modifies acomposition of the duty cycle of one or more sequentially arrangedoptical elements.
 6. The system of claim 1, wherein one or more opticalelement of the set of sequentially-arranged optical elements spends aportion of a duty cycle steering the at least some of the light from thefirst subset to the second subset to increase the dynamic range of theimage.
 7. The system of claim 2, wherein the intermediary opticalelement comprises an array of integrating rods arranged to correspond tothe plurality of illumination zones.
 8. The system of claim 6, whereinthe portion of the duty cycle corresponds to a light intensity level ofa light intensity zone of the image.
 9. The system of claim 1, whereinthe set of sequentially-arranged optical elements comprises one or morerotatable mirrors.
 10. The system of claim 7, wherein at least one ofthe one or more rotatable mirrors is mounted on a gimbal.
 11. The systemof claim 1, wherein the set of sequentially-arranged optical elementscomprises one or more digital micro-mirror devices.
 12. The system ofclaim 1 further comprising: a drive system for configuring the spatiallight modulator to produce the image based on image content data; andwherein the drive system configures the set of sequentially-arrangedoptical elements to steer the light to the plurality of illuminationzones of the spatial light modulator based on the image content data.13. The system of claim 1, wherein the light source comprises a laserlight module.
 14. The system of claim 1, wherein the light sourcecomprises a lamp.
 15. The system of claim 1, wherein the light sourcecomprises at least one of a light emitting diode and a laser-phosphorhybrid light source.
 16. The system of claim 1 further comprising lightcollimating optics.
 17. The system of claim 1, wherein the spatial lightmodulator comprises a digital micromirror device.
 18. The system ofclaim 1, wherein the spatial light modulator comprises a liquid crystaldevice.
 19. A method for producing an image having high dynamic range,comprising: providing light along an optical path; steering the light byone or more sequentially arranged optical elements to increase thedynamic range of an image; and directing the light to produce an image.20. The method of claim 19, the steering further comprising modifying adwell time of the one or more sequentially arranged optical elements.21. The method of claim 19 further comprising modifying a composition ofthe duty cycle of one or more sequentially arranged optical elements.